A conducting spherical shell of radius R is cut in half. The two hemispherical pieces are electrically separated from each other but are left close together, so that the distance separating the two halves may be neglected. The upper half is maintained at Phi=Phi0 and the lower half is maintained at phi=0. Find the electrostatic potential phi at all points in space outside of the surface of the conductors. You may neglect 1/r^4.